1. Field of the Invention
The present invention relates to a communication message conversion apparatus and a communication message conversion method of converting messages between communication networks of different protocol, and in particular relates to a communication message conversion apparatus and a communication message conversion method suitable for message conversion between a FlexRay network (registered trademark of Daimler Chrysler AG) and a CAN (Controller Area Network).
2. Description of the Related Art
According to replacement an equipment mounted in vehicles to an electronic equipment, communication networks are also being constructed within vehicles. CANs (Controller Area Networks) are widely employed for such vehicle LANs (Local Area Networks) (see for example Laid-open Japanese Patent Application No. 2003-264576).
On the other hand, with increase in the amount of data and increased complexity, networks of higher speed and reliability are being demanded. For this purpose, attention has been focused on FlexRay® as a high-speed network. The maximum transfer rate of FlexRay is 10 Mbps, which is 10 times the 1 Mbps which is the maximum transfer rate of CAN.
Thus, in introduction of FlexRay, it has become necessary to consider communication with the previously employed CAN. Message conversion apparatus that can perform communication conversion between FlexRay and CAN has therefore been proposed (see for example Laid-open Japanese Patent Application No. 2005-328119 (FIG. 2).
In this message conversion apparatus that has been proposed, a CPU (central processing unit) is provided between the FlexRay controller that is connected with the FlexRay network and the CAN controller that is connected with the CAN network. By software processing, this CPU converts messages from the CAN controller to FlexRay messages in accordance with the FlexRay protocol and transmits these to the FlexRay controller, and converts messages from the FlexRay controller to CAN messages in accordance with the CAN protocol, and transmits these to the CAN controller.
However, in the conventional message conversion apparatus, this function was implemented by software. Consequently, if the CPU was allocated processing functions apart from conversion processing and routing processing, the load on the CPU became large causing delay in conversion, making it difficult to utilize the high-speed transfer rate effectively. In particular, as the communication protocols of FlexRay and CAN are different, it is necessary to perform synchronous monitoring, error monitoring and error processing in a high priority, so it is inevitable increased on the CPU load.
Also, with regard to conversion processing and routing processing, when the number of FlexRay or CAN channels is increased, considerable time is required for channel retrieval at the relay destination, with the result that routing processing takes a considerable time. Furthermore, since there is an increase in the number of frames requiring conversion processing, the latency time in the conversion apparatus is increased, tending to have an adverse effect on throughput and making a large-capacity buffer memory necessary.